Chapter 39 powerpoint


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Chapter 39 powerpoint

  1. 1. <ul><li>Chapter 39 ~ Plant Responses to Internal and External Signals </li></ul>
  2. 2. Plant hormones <ul><li>Hormone: chemical signals that coordinate parts of an organism; produced in one part of the body and then transported to other parts of the body; low concentrations </li></ul><ul><li>Tropism: movement toward or away from a stimulus </li></ul><ul><li>Went experiments (phototropism) </li></ul><ul><li>Hormone: auxin </li></ul><ul><li>Others: gravitropism, thigmotropism </li></ul>
  3. 3. Auxin <ul><li>IAA (indoleacetic acid) </li></ul><ul><li>Location: seed embryo; meristems of apical buds and young leaves </li></ul><ul><li>Function: stem elongation; root growth, differentiation, branching; fruit development; apical dominance; tropisms </li></ul>
  4. 4. Cytokinins <ul><li>Zeatin </li></ul><ul><li>Location: roots (and actively growing tissues) </li></ul><ul><li>Function: root growth and differentiation; cell division and growth; germination; delay senescence (aging); apical dominance (w/ auxin) </li></ul>
  5. 5. Gibberellins <ul><li>GA 3 </li></ul><ul><li>Location: meristems of apical buds and roots, young leaves, embryo </li></ul><ul><li>Function: germination of seed and bud; stem elongation; leaf growth; flowering (bolting); fruit development; root growth and differentiation </li></ul>
  6. 6. Abscisic acid <ul><li>ABA </li></ul><ul><li>Location: leaves, stems, roots, green fruit </li></ul><ul><li>Function: inhibits growth; closes stomata during stress; counteracts breaking of dormancy </li></ul>
  7. 7. Ethylene <ul><li>Gaseous hormone </li></ul><ul><li>Location: ripening fruit tissue; stem nodes; aging leaves and flowers </li></ul><ul><li>Function: fruit ripening; oppositional to auxin (leaf abscission); promotes/inhibits: growth/development of roots, leaves, and flowers; senescence </li></ul>
  8. 8. Daily and Seasonal Responses <ul><li>Circadian rhythm (24 hour periodicity) </li></ul><ul><li>Photoperiodism (phytochromes) </li></ul><ul><li>Short-day plant : light period shorter than a critical length to flower (flower in late summer, fall, or winter; poinsettias, chrysanthemums) </li></ul><ul><li>Long-day plant : light period longer than a critical length to flower (flower in late spring or early summer; spinach, radish, lettuce, iris) </li></ul><ul><li>Day-neutral plant : unaffected by photoperiod (tomatoes, rice, dandelions) </li></ul><ul><li>Critical night length controls flowering </li></ul>
  9. 9. Phytochromes <ul><li>Plant pigment that measures length of darkness in a photoperiod (red light) </li></ul><ul><li>P r (red absorbing) 660nm </li></ul><ul><li>P fr (far-red absorbing) 730nm </li></ul>